There are three main groups of rock drilling methods: percussive, rotary crushing and cutting rock drilling. In percussive and rotary crushing rock drilling, the inserts generally have a rounded shape, often a cylinder with a rounded top surface generally referred to as a button. In rotary cutting rock drilling, the inserts are provided with an edge which acts as a cutter.
The inserts for metal cutting are provided with a sharp edge which acts as a cutter. The bodies for various types of wear part applications have different non-cutting configurations. There already exists a number of such high pressure-high temperature sintered buttons, inserts and bodies of cemented carbide provided with polycrystalline diamond bodies or layers.
The technique when producing such polycrystalline diamond tools using high pressure/high temperature where diamond is the stable phase has been described in a number of patents, e.g., U.S. Pat. No. 2,941,248, "High Temperature High Pressure Apparatus". U.S. Pat. No. 3,141,746, "Diamond Compact Abrasive". High pressure bonded body having more than 50 vol % diamond and a metal binder: Co, Ni, Ti, Cr, Mn, Ta, etc. These patents disclose the use of a pressure and a temperature where diamond is the stable phase.
In some later patents, e.g., U.S. Pat. Nos. 4,764,434 and 4,766,040, high pressure-high temperature sintered polycrystalline diamond tools are described. In the first patent, the diamond layer is bonded to a support body having a complex, non-plane geometry by means of a thin layer of a refractory material applied by PVD- or CVD-technique. In the second patent, temperature resistant abrasive polycrystalline diamond bodies are described having different additions of binder metals at different distances from the working surface.
A recent development in this field is the use of one or more continuous layers of polycrystalline diamond on the top surface of the cemented carbide button. U.S. Pat. No. 4,811,801, discloses rock bit buttons including such a polycrystalline diamond surface on top of the cemented carbide buttons.
Another development is disclosed in U.S. Pat. No. 4,592,433, including a cutting blank for use on a drill bit comprising a substrate of a hard material having a cutting surface with strips of polycrystalline diamond dispersed in grooves arranged in various patterns.
U.S. Pat. No. 4,784,023, discloses a cutting element comprising a stud and a composite bonded thereto. The composite comprises a substrate formed of cemented carbide and a diamond layer bonded to a substrate. The interface between the diamond layer and the substrate is defined by alternating ridges of diamond and cemented carbide which are mutually interlocked. The top surface of the diamond body is continuous and covering the whole insert. The sides of the diamond body are not in direct contact with any cemented carbide.
U.S. Pat. No. 4,819,516, discloses cutting element with a V-shaped diamond cutting face. The cutting element is formed from a single circular cutting blank by cutting the blank into segments joining two identical ones of the segments and truncating the joined segments. Also in this case, the surface of the diamond body is continuous and the sides are not in direct contact with any cemented carbide.
European Patent Application No. 0312281, discloses a tool insert comprising a body of cemented carbide with a layer of polycrystalline diamond and between the layer and the cemented carbide, a number of recesses filled with abrasive compact material extending into the supporting body of cemented carbide.
U.S. Pat. No. 4,871,377, discloses a composite compact including a table of diamond particles with a strong, chemically inert binder matrix and a thin metal layer bonded directly to the table in a HP/HT press.
Another development in this field is the use of cemented carbide bodies having different structures in different distances from the surface, such as disclosed in U.S. Pat. Nos. 4,743,515 and 4,843,039, where bodies of cemented carbide containing eta-phase are surrounded by a surface zone of cemented carbide free of eta-phase and having a low content of cobalt in the surface and a higher content of cobalt closer to the eta-phase zone. U.S. Pat. No. 4,820,482, discloses rock bit buttons of cemented carbide having a content of binder phase in the surface that is lower and in the center higher than the nominal content. In the center, there is a zone having a uniform content of binder phase. The tungsten carbide grain size is uniform throughout the body.